09-05-2011, 12:09 PM
Abstract :
The advent of microprocessors has opened up several product opportunities
that simply did not exist earlier. These intelligent processors have invaded and
embedded themselves into all fields of our lives be it the kitchen (food processors,
microwave ovens), the living rooms (televisions, airconditioners) or the work places (fax
machines, pagers, laser printer, credit card readers) …etc.
As the complexities in the embedded applications increase, use of an operating
system brings in lot of advantages. Most embedded systems also have real-time
requirements demanding the use of Real time Operating Systems (RTOS) capable of
meeting the embedded system requirements. Real-time Operating System allows realtime
applications to be designed and expanded easily. The use of an RTOS simplifies the
design process by splitting the application code into separate tasks. An RTOS allows one
to make better use of the system recourses by providing with valuable services such as
semaphores, mailboxes, queues, time delays, time outs…etc.
This report looks at the basic concepts of embedded systems, operating systems and
specifically at Real Time Operating Systems in order to identify the features one has to
look for in an RTOS before it is used in a real-time embedded application. Some of the
popular RTOS have been discussed in brief, giving their salient features, which make
them suitable for different applications.
I. INTRODUCTION
Last few decades have seen the rise of computers to a position of prevalence in human
affairs. It has made its mark in every field ranging personal home affairs, business, process
automation in industries, communications, entertainment, defense etc...
An embedded system is a combination of hardware and software and perhaps other
mechanical parts designed to perform a specific function. Microwave oven is a good example
of one such system. This is in direct contrast to a personal computer. Though it is also
comprised of hardware and software and mechanical components it is not designed for a
specific purpose. Personal computer is general purpose and is able to do many different
things.
An embedded system is generally a system within a larger system. Modern cars and
trucks contain many embedded systems. One embedded system controls anti-lock brakes,
another monitors and controls vehicle’s emission and a third displays information on the
dashboard. Even the general-purpose personal computer itself is made up of numerous
embedded systems. Keyboard, mouse, video card, modem, hard drive, floppy drive and sound
card are each an embedded system.
Tracing back the history, the birth of microprocessor in 1971 marked the booming of
digital era. Early embedded applications included unmanned space probes, computerized
traffic lights and aircraft flight control systems. In the 1980s, embedded systems brought
microprocessors into every part of our personal and professional lives. Presently there are
numerous gadgets coming out to make our life easier and comfortable because of advances in
embedded systems. Mobile phones, personal digital assistants and digital cameras are only a
small segment of this emerging field [2].
One major subclass of embedded systems is real-time embedded systems. A real timesystem
is one that has timing constraints. Real-time system’s performance is specified in
terms of ability to make calculations or decisions in a timely manner. These important
calculations have deadlines for completion. A missed deadline is just as bad as a wrong
answer. The damage caused by this miss will depend on the application. For example if the
real-time system is a part of an airplane’s flight control system, single missed deadline is
sufficient to endanger the lives of the passengers and crew.
II. INSIDE AN EMBEDDED SYSTEM
All embedded systems contain a processor and software. The processor may be 8051
micro-controller or a Pentium-IV processor (having a clock speed of 2.4 GHz). Certainly , in
order to have software there must be a place to store the executable code and temporary
storage for run-time data manipulations. These take the form of ROM and RAM respectively.
If memory requirement is small, it may be contained in the same chip as the processor.
Otherwise one or both types of memory will reside in external memory chips. All embedded
systems also contain some type of inputs and outputs (Fig. 1). For example in a microwave
oven the inputs are the buttons on the front panel and a temperature probe and the outputs are
the human readable display and the microwave radiation. Inputs to the system generally take
the form of sensors and probes, communication signals, or control knobs and buttons. Outputs
are generally displays, communication signals, or changes to the physical world.
Download full report
http://citeseerx.ist.psu.edu/viewdoc/dow...1&type=pdf
The advent of microprocessors has opened up several product opportunities
that simply did not exist earlier. These intelligent processors have invaded and
embedded themselves into all fields of our lives be it the kitchen (food processors,
microwave ovens), the living rooms (televisions, airconditioners) or the work places (fax
machines, pagers, laser printer, credit card readers) …etc.
As the complexities in the embedded applications increase, use of an operating
system brings in lot of advantages. Most embedded systems also have real-time
requirements demanding the use of Real time Operating Systems (RTOS) capable of
meeting the embedded system requirements. Real-time Operating System allows realtime
applications to be designed and expanded easily. The use of an RTOS simplifies the
design process by splitting the application code into separate tasks. An RTOS allows one
to make better use of the system recourses by providing with valuable services such as
semaphores, mailboxes, queues, time delays, time outs…etc.
This report looks at the basic concepts of embedded systems, operating systems and
specifically at Real Time Operating Systems in order to identify the features one has to
look for in an RTOS before it is used in a real-time embedded application. Some of the
popular RTOS have been discussed in brief, giving their salient features, which make
them suitable for different applications.
I. INTRODUCTION
Last few decades have seen the rise of computers to a position of prevalence in human
affairs. It has made its mark in every field ranging personal home affairs, business, process
automation in industries, communications, entertainment, defense etc...
An embedded system is a combination of hardware and software and perhaps other
mechanical parts designed to perform a specific function. Microwave oven is a good example
of one such system. This is in direct contrast to a personal computer. Though it is also
comprised of hardware and software and mechanical components it is not designed for a
specific purpose. Personal computer is general purpose and is able to do many different
things.
An embedded system is generally a system within a larger system. Modern cars and
trucks contain many embedded systems. One embedded system controls anti-lock brakes,
another monitors and controls vehicle’s emission and a third displays information on the
dashboard. Even the general-purpose personal computer itself is made up of numerous
embedded systems. Keyboard, mouse, video card, modem, hard drive, floppy drive and sound
card are each an embedded system.
Tracing back the history, the birth of microprocessor in 1971 marked the booming of
digital era. Early embedded applications included unmanned space probes, computerized
traffic lights and aircraft flight control systems. In the 1980s, embedded systems brought
microprocessors into every part of our personal and professional lives. Presently there are
numerous gadgets coming out to make our life easier and comfortable because of advances in
embedded systems. Mobile phones, personal digital assistants and digital cameras are only a
small segment of this emerging field [2].
One major subclass of embedded systems is real-time embedded systems. A real timesystem
is one that has timing constraints. Real-time system’s performance is specified in
terms of ability to make calculations or decisions in a timely manner. These important
calculations have deadlines for completion. A missed deadline is just as bad as a wrong
answer. The damage caused by this miss will depend on the application. For example if the
real-time system is a part of an airplane’s flight control system, single missed deadline is
sufficient to endanger the lives of the passengers and crew.
II. INSIDE AN EMBEDDED SYSTEM
All embedded systems contain a processor and software. The processor may be 8051
micro-controller or a Pentium-IV processor (having a clock speed of 2.4 GHz). Certainly , in
order to have software there must be a place to store the executable code and temporary
storage for run-time data manipulations. These take the form of ROM and RAM respectively.
If memory requirement is small, it may be contained in the same chip as the processor.
Otherwise one or both types of memory will reside in external memory chips. All embedded
systems also contain some type of inputs and outputs (Fig. 1). For example in a microwave
oven the inputs are the buttons on the front panel and a temperature probe and the outputs are
the human readable display and the microwave radiation. Inputs to the system generally take
the form of sensors and probes, communication signals, or control knobs and buttons. Outputs
are generally displays, communication signals, or changes to the physical world.
Download full report
http://citeseerx.ist.psu.edu/viewdoc/dow...1&type=pdf